This invention relates to a substrate material for a magnetic head and a magnetic head using it.
Ferrite has been conventionally widely used as a core material for a magnetic head due to its excellent machinability and wear resistance. However, its saturation magnetization is lower than alloy materials by 30 to 50 percent.
Therefore, when ferrite is used with high-density recording tapes having a high coercive force, which have been developed in recent years, the low saturation magnetization of the ferrite head core material is a problem, and the ferrite head has a poor S/N as compared with metal heads, since it causes a large rubbing noise during a tape running.
From the above viewpoint, Sendust and amorphous metal magnetic materials are used as a core material in a head for high density recording media.
A head using a metal magnetic material has a so-called sandwich structure as shown in FIG. 3, in which a metal magnetic material 4 of a tape-running surface having a gap 5 is placed between nonmagnetic substrate materials 3. In this case, the-nonmagnetic substrate material is made of crystallization glass.
The problem in this case is partial abrasion between a substrate 1 and a metal magnetic material 2 when a tape runs, as is schematically shown in FIG. 4. That is, the magnetic material is suffered partial abrasion relative to the substrate, and a head output is hence decreased due to spacing loss. For this reason, performances of the substrate and metal magnetic materials such as coefficient of thermal expansion, etc., are required to be in agreement.
In order to overcome such a problem, calcium titanate (CaTiO.sub.3)-based ceramic materials have been proposed as a substrate material for a magnetic head for use with high-density recording media, a metal evaporated tape in particular.
However, a ceramic substrate composed of such a material has very poor machinability. And, for example, the rate for cutting it with a diamond cutter is as poor as 1/5 to 1/10 of that for cutting a ferrite material, and mass-production of magnetic heads therefrom has been difficult.
It is an object of this invention to provide a substrate material for a magnetic head having a so-called sandwich structure of placement of a metal magnetic material between nonmagnetic substrate materials, which causes little partial abrasion between the substrate and the metal magnetic material when a tape runs, or is free from a decrease in head output caused by spacing loss when the magnetic material is suffered partial abrasion relative to the substrate, and which has excellent machinability, and a magnetic head using said substrate material.